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Advanced Aquarium Concepts

Nature is Not Always Ideal

Many people look to nature to inspire their captive care of fish and other animals with the assumption that this is inherently the ideal care for those animals. I feel that nature is indeed a good start and needs to be considered. However, I firmly believe that the methods of nature are not the ideal for captive animals.

There are many things in nature that are indeed very hard on the fish. These things include malnutrition, starvation, natural disasters, predation, pathogens, and many others. Nature is not a nice place to be for an individual, it is very demanding and functions to weed out as many individuals as possible.

Predation is a major factor. It functions to weed out slow (physically or mentally), over- or underweight individuals, any individuals with almost any deformity, the young, the old, the weak, the sick, and the noticeable (brightly colored males for example). All of this helps to make a stronger population, but for the individual this is not a good thing. Many of the individuals that become prey before a ripe old age do so because they are sick.

Illness is a major factor in the success of an individual. What starts as a minor infection can open the individual up to other illnesses. This can end up slowing down and weakening the individual. This makes them very easy prey for predators. Most sick animals end up as prey before the disease itself would have killed them. Even if the animal does not become prey because of the disease or die from it directly, it can still suffer in other ways. The physical damage done by certain diseases can slow them down or cause deformities, both of which make the individual more likely to end up as prey later on.

Diet is another major issue. We simply cannot simulate the natural diet of most fish. These animals have 24 hours a day, 7 days a week to forage for food. Even if I was doing research in Amazonia on native fishes, had a bunch in some research facility, was working with a native tribe and they went out and gathered food for four hours every day, I still would not be replicating their natural diet. We may be able to study the stomach content analysis from wild caught individuals, but we have no idea that they are not also occasionally coming across other foods at a much less frequent rate, possibly with vital micronutrients or some other vital part of their diet. In addition, in the wild the foods available change throughout the year and even year to year. During the beginning of the rainy season certain terrestrial animals become a large part of the diet of many if not most fish. The rain literally washes a number of animals and other food items into the waters for the fish to gorge on. In addition to this variability, different foods are available at different parts of the day. This will be more likely to be known from observation and stomach content analysis, but there is still going to be some unknown variability here.

Our ‘natural’ diets are far from it. These diets are usually described as live foods (feeder fish, many types of worms, assorted invertebrates, etc.), frozen foods (beef heart, squid, brine shrimp, etc.), freeze-dried, and even many processed foods are marketed as natural. Some brands toss in things like fresh seafood, kelp, and other similar ingredients. The most common argument is ‘this is the type of stuff they would eat in the wild’. Neon tetras, discus, etc. do not naturally eat kelp and salmon. No fish naturally feasts on beef heart. These food items are no more natural to these fish than the ingredients in the processed foods that so many avoid because they are supposedly so unnatural. Goldfish are not found in the natural waters of Oscars. It is totally unnatural for them to eat goldfish. These foods may be similar, but it is not as natural as many may think they are.

On top of all of that there is no guarantee that what they eat in the wild is actually the ideal diet. Remember that one thing nature is always doing is trying to take out as many individuals as possible. The diet itself may be minimal for the individuals who are the best foragers and who have the best digestive systems. This means that the individuals who are less than the best may not be getting a good enough diet and this could be contributing to their weak nature, impaired immune system, etc. which can lead to them becoming prey.

Another major issue is reproduction. There are many styles of reproduction, lots of small eggs, few large eggs, live birth, etc. They all have benefits and consequences. But one thing that all of these have in common is that many more offspring are produced than have any chance of surviving. What this means is that the already mentioned issues in addition to many others are doing their best to remove individuals from the population (kill them). Even out of the ones that do make it to maturity not all will reproduce. Out of the ones that do reproduce not all will do so successfully. Success is based on the offspring’s ability to reproduce successfully. For example, convict cichlids can have hundreds of fry per brood. They can have multiple broods in a single year. They can live for many years. This allows for the potential for well over a thousand offspring in a single pair’s life. Breaking even the pair will produce two offspring that will end up successfully reproducing. Two offspring that will replace the two breeding adults is breaking even. Any less is a deficit and any more is surplus and therefore very successful. If we tried to simulate this we would be going through hundreds if not thousands of individuals in order to pick the right ones to breed.

In the end nature wants very few individuals to make it, literally a small fraction of one percent. We on the other hand want a much higher success rate than this. We want every single one of the fish we go out and spend our hard earned money on to make it to adulthood.

Nature is where they come from. It is what they have adapted to and what has dictated their every evolutionary step. It is a great place to start, especially when little or no other information is available. However, it is not the ideal. It is not the end. When we keep these animals in captivity it is a completely different story. We need to make sure that we do what is best for our individual animals, even if it completely contradicts what would happen in nature.


If you have any questions or comments please feel free to contact Brian directly at:
Brian@BriansAquariumCare.com or Email Brian Now